The main thrust of our laboratory for the past 25 years has been the study of the structure and function of the major histocompatibility complex. Our primary focus has been in the genetics of the rat MHC, although we have done a substantial amount of work on the human MHC as well. We are now trying to isolate the class I genes that are linked to the MHC, since they are critical markers for genes in this region that effect both development and susceptibility to cancer. It is critical for us to be able to compare gene sequences of our class I genes with those of the mouse and the human. It will be even more important when we begin to search for open reading frames in the MHC-linked region to determine whether it contains any genes that affect growth and that may have already been defined and listed in Genebank.